1. Field of the Invention
This invention relates to bending of glass sheets brought to the deformation temperature, the sheets moving in horizontal or approximately horizontal position on a shaping bed made up of rotating shaping elements. The disclosure of this application is related to that of U.S. patent application Ser. No. 669,795, filed on the same date as the present application by the present Applicants and entitled "DEVICE FOR BENDING GLASS SHEETS".
2. Description of the Prior Art
Such a bending technique is described in French Pat. No. 2,312,463. Glass sheets advance on a shaping bed consisting of curved rods surrounded by deformable sheaths which are rotatably driven. These rods are progressively and increasingly raised to progressively bend the sheets until they have a cylindrical shape. This type of bending is particularly easy to obtain, the installation easy to handle and the output is high.
French Pat. No. 2,442,219 describes an installation derived from that described above, in which the glass sheets acquire a double bending, i.e., a crosswise bending of the type described above, by fitting the sheets to the profile of curved rods identical with those described above, placed crosswise to the direction of the sheets' advance. A lengthwise bending, i.e., in the direction of sheet advance is also provided, because the curved rods are placed one after the other in the direction of advance of the glass sheets, in a curved profile. This results in a double bending, in other words, a spherical bending for the glass sheets.
These known processes and devices do not make it possible to bend glass sheets except in a purely cylindrical or purely spherical configuration.
Further, since the amount of curvature of the glass sheets is a direct function of the configuration of the installation--inclination of the curved rods, profile of the lengthwise curvature, etc.--obtaining very precisely determined curvatures requires a precision and monitoring of the rod configurations all along the bending station.